Audio Guide：

The Big Bang Theory is the most widely accepted theory regarding the origin of the universes. It states that the universe began at the initial singularity, which is extremely high in density and temperature. The universe was born at the instant of explosion. At first, the temperature in the universe was so high that only photons and elementary particles with extremely high energy existed. As the universe expanded, the temperature gradually declined. Elementary particles formed the nuclei of hydrogen and helium. 380,000 years later, atoms formed, and galaxies, stars, and planets began to emerge. Hubble’s Law, the cosmic microwave background, and helium’s abundance are all evidence that point to the validity of the Big Bang Theory.